install_deps.sh: first attempt to support cxx11.

For now, we merely add an option that sets CXXFLAGS envvar with
'--std=c++11' option.

There is no check done to ensure compatibility with the system
libraries, mainly because:
  - It is all but trivial to get this information in a generic and
    reliable way.
  - Currently even cutting edge distributions may still distribute some c++98
    libraries.
  - With recent stdlibc++, both ABIs are supported together, which means
    that incompatibilities are rather unlikely.

To summarize: if your system is recent and built with gcc-5.1 or more,
you should not experience too much troubles with c++11.

build_files/build_environment/install_deps.sh

@@ -25,7 +25,8 @@
 ARGS=$( \
 getopt \
 -o s:i:t:h \
---long source:,install:,tmp:,info:,threads:,help,show-deps,no-sudo,no-build,no-confirm,with-all,with-opencollada,\
+--long source:,install:,tmp:,info:,threads:,help,show-deps,no-sudo,no-build,no-confirm,use-cxx11,\
+with-all,with-opencollada,\
 ver-ocio:,ver-oiio:,ver-llvm:,ver-osl:,ver-osd:,ver-openvdb:,\
 force-all,force-python,force-numpy,force-boost,\
 force-ocio,force-openexr,force-oiio,force-llvm,force-osl,force-osd,force-openvdb,\
@@ -103,6 +104,11 @@ ARGUMENTS_INFO="\"COMMAND LINE ARGUMENTS:
     --no-confirm
         Disable any interaction with user (suitable for automated run).
 
+    --use-cxx11
+        Build all libraries in cpp11 'mode' (will be mandatory soon in blender2.8 branch).
+        NOTE: If your compiler is gcc-6.0 or above, you probably *want* to enable this option (since it's default
+              standard starting from this version).
+
     --with-all
         By default, a number of optional and not-so-often needed libraries are not installed.
         This option will try to install them, at the cost of potential conflicts (depending on
@@ -281,6 +287,7 @@ SUDO="sudo"
 
 NO_BUILD=false
 NO_CONFIRM=false
+USE_CXX11=false
 
 PYTHON_VERSION="3.5.1"
 PYTHON_VERSION_MIN="3.5"
@@ -492,6 +499,9 @@ while true; do
     --no-confirm)
       NO_CONFIRM=true; shift; continue
     ;;
+    --use-cxx11)
+      USE_CXX11=true; shift; continue
+    ;;
     --with-all)
       WITH_ALL=true; shift; continue
     ;;
@@ -766,7 +776,18 @@ OPENCOLLADA_REPO_BRANCH="master"
 
 FFMPEG_SOURCE=( "http://ffmpeg.org/releases/ffmpeg-$FFMPEG_VERSION.tar.bz2" )
 
+CXXFLAGS_BACK=$CXXFLAGS
+if [ "$USE_CXX11" = true ]; then
+  WARNING "You are trying to use c++11, this *should* go smoothely with any very recent distribution
+However, if you are experiencing linking errors (also when building Blender itself), please try the following:
+    * Re-run this script with `--build-all --force-all` options.
+    * Ensure your gcc version is at the very least 4.8, if possible you should really rather use gcc-5.1 or above.
 
+Please note that until the transition to C++11-built libraries if completed in your distribution, situation will
+remain fuzzy and incompatibilities may happen..."
+  CXXFLAGS="$CXXFLAGS -std=c++11"
+  export CXXFLAGS
+fi
 
 #### Show Dependencies ####
 
@@ -953,7 +974,7 @@ prepare_opt() {
 
 # Check whether the current package needs to be recompiled, based on a dummy file containing a magic number in its name...
 magic_compile_check() {
-  if [ -f $INST/.$1-magiccheck-$2 ]; then
+  if [ -f $INST/.$1-magiccheck-$2-$USE_CXX11 ]; then
     return 0
   else
     return 1
@@ -962,7 +983,7 @@ magic_compile_check() {
 
 magic_compile_set() {
   rm -f $INST/.$1-magiccheck-*
-  touch $INST/.$1-magiccheck-$2
+  touch $INST/.$1-magiccheck-$2-$USE_CXX11
 }
 
 # Note: should clean nicely in $INST, but not in $SRC, when we switch to a new version of a lib...
@@ -1622,6 +1643,10 @@ compile_OIIO() {
 #    fi
     cmake_d="$cmake_d -D USE_OCIO=OFF"
 
+    if [ "$USE_CXX11" = true ]; then
+      cmake_d="$cmake_d -D OIIO_BUILD_CPP11=ON"
+    fi
+
     if file /bin/cp | grep -q '32-bit'; then
       cflags="-fPIC -m32 -march=i686"
     else
@@ -4164,6 +4189,12 @@ print_info() {
   _buildargs="$_buildargs -U *OPENCOLORIO* -U *OPENEXR* -U *OPENIMAGEIO* -U *LLVM* -U *CYCLES*"
   _buildargs="$_buildargs -U *OPENSUBDIV* -U *OPENVDB* -U *COLLADA* -U *FFMPEG* -U *ALEMBIC*"
 
+  if [ "$USE_CXX11" = true ]; then
+    _1="-D WITH_CXX11=ON"
+    PRINT "  $_1"
+    _buildargs="$_buildargs $_1"
+  fi
+
   _1="-D WITH_CODEC_SNDFILE=ON"
   PRINT "  $_1"
   _buildargs="$_buildargs $_1"
@@ -4327,3 +4358,6 @@ PRINT ""
 # Switch back to user language.
 LANG=LANG_BACK
 export LANG
+
+CXXFLAGS=$CXXFLAGS_BACK
+export CXXFLAGS